Functionalized elastomer containing a boron group

ABSTRACT

The present invention is directed to a copolymer of 1,3-butadiene or isoprene and a monomer of formula I or V 
                         
wherein R 1  is a covalent bond, phenylene, a linear or branched alkane diyl group containing 1 to 10 carbon atoms, or a combination of one or more phenylene groups and one or more linear or branched alkane diyl groups containing 1 to 10 carbon atoms; R 2  and R 3  are independently linear or branched alkyl groups containing 1 to 10 carbon atoms; or R 5  is a linear or branched alkane diyl group containing 1 to 20 carbon atoms, or a bridging aromatic group. The invention is further directed to a rubber composition including the copolymer, and a pneumatic tire containing the rubber composition. The invention is further directed to a method of making such a copolymer.

BACKGROUND

Stereoregular diene polymers are produced and used industrially on alarge scale as an important component of tire compounds. Diene polymerswith high levels of stereoregularity are almost exclusively preparedwith coordination polymerization catalysts, which are in general easilypoisoned by polar functionalities. Because of this poisoning effect, thetypes of monomers that are compatible with coordination catalysts areusually limited to simple hydrocarbons. It is well known within the tireindustry that the incorporation of even low levels of functionality intocertain tire polymers (prepared through anionic or emulsionpolymerization) significantly improves the performance of tirescontaining such polymers. Unfortunately, there is currently no reliablemethod to apply this functionalization technology to stereoregular dienepolymers, but it is likely that such a polymer would show superior tireproperties over known unfunctionalized polymers.

EP189174 discloses polymerization and copolymerization of2-alkoxysilyl-1,3-butadiene monomers.

WO2004/007602 discloses a catalyst for the polymerization of 1,4-dienes,styrene and for the copolymerization of two monomers. Thecharacteristics of the inventive catalyst include a high degree ofstereoselectivity, catalytic activity and tolerance to the presence ofpolar impurities. Said catalyst combines the characteristics specific toNi-based diene polymerization catalysts (high stereoselectivity andcatalytic activity) with a well-defined character and tolerance to thepresence of polar substances.

Sunada et al. (Journal of Applied Polymer Science, Vol. 97, 1545-1552(2005) disclose triethoxysilyl-modified polychloroprene (CR) latexsynthesized by the emulsion copolymerization of2-(3-triethoxysilypropyl)-1,3-butadiene with chloroprene.

U.S. Pat. No. 8,063,152 discloses functionalizing agents that areparticularly useful for functionalizing living rubbery polymers to makethe polymer more compatible with fillers, such as carbon black andsilica. These functionalizing agents are comprised of a boron containingcompound having a structural formula selected from the group consistingof:

wherein R is selected from the group consisting of hydrogen atoms, alkylgroups and aryl groups, wherein R¹, R², and R³ can be the same ordifferent and are selected from the group consisting of alkyl groups,and aryl groups, and wherein R⁴ represents an alkylene group or abridging aromatic group.

SUMMARY

The present invention is directed to a copolymer of 1,3-butadiene orisoprene and a monomer of formula I or II

wherein R¹ is a covalent bond, phenylene, a linear or branched alkanediyl group containing 1 to 10 carbon atoms, or a combination of one ormore phenylene groups and one or more linear or branched alkane diylgroups containing 1 to 10 carbon atoms; R² and R³ are independentlylinear or branched alkyl groups containing 1 to 10 carbon atoms; or R⁵is a linear or branched alkane diyl group containing 1 to 20 carbonatoms, or a bridging aromatic group.

The invention is further directed to a rubber composition including thecopolymer, and a pneumatic tire containing the rubber composition.

The invention is further directed to a method of making such acopolymer.

DESCRIPTION

There is disclosed a copolymer of 1,3-butadiene or isoprene and amonomer of formula I or II

wherein R¹ is a covalent bond, phenylene, a linear or branched alkanediyl group containing 1 to 10 carbon atoms, or a combination of one ormore phenylene groups and one or more linear or branched alkane diylgroups containing 1 to 10 carbon atoms; R² and R³ are independentlylinear or branched alkyl groups containing 1 to 10 carbon atoms; or R⁵is a linear or branched alkane diyl group containing 1 to 20 carbonatoms, or a bridging aromatic group.

There is further disclosed a rubber composition including the copolymer,and a pneumatic tire containing the rubber composition.

There is further disclosed a method of making such a copolymer.

The copolymer is produced via polymerization of a nonfunctionalizeddiene monomer and a functionalized diene monomer.

In one embodiment, the nonfunctionalized diene monomer is 1,3-butadieneor isoprene. In one embodiment, the functionalized diene monomer is amonomer of formula I or II

wherein R¹ is a covalent bond, phenylene, a linear or branched alkanediyl group containing 1 to 10 carbon atoms, or a combination of one ormore phenylene groups and one or more linear or branched alkane diylgroups containing 1 to 10 carbon atoms; R² and R³ are independentlylinear or branched alkyl groups containing 1 to 10 carbon atoms; or R⁵is a linear or branched alkane diyl group containing 1 to 20 carbonatoms, or a bridging aromatic group.

In one embodiment, bridging aromatic group is selected from one of thefollowing structures:

The copolymer has a high degree of stereoregularity. In one embodiment,the copolymer has a cis 1,4 microstructure content of greater than 80percent by weight based on the polybutadiene content of the copolymer.In one embodiment, the copolymer has a cis 1,4 microstructure content ofgreater than 95 percent by weight based on the polybutadiene content ofthe copolymer.

The copolymer has a major weight portion attributed to units derivedfrom the nonfunctionalized monomer, and a minor weight portionattributed to units derived from the functionalized monomer. In oneembodiment, the copolymer comprises from 0.1 to 40 percent by weight ofunits derived from the functionalized diene monomer. In one embodiment,the copolymer comprises from 0.5 to 20 percent by weight of unitsderived from the functionalized diene monomer. In one embodiment, thecopolymer comprises from 1 to 5 percent by weight of units derived fromthe functionalized diene monomer.

The copolymer is produced by polymerization of the nonfunctionalizedmonomer and functionalized monomer in the presence of a nickelcoordination catalyst. In one embodiment, the catalyst is an(allyl)(arene)Ni(II) compound. Suitable (allyl)(arene)Ni(II) compoundsmay be produced as described in O'Connor et al. (Organometallics 2009,28 2372-2384). The catalyst is generally in the form of a cation with asuitable counteranion. In one embodiment, the counteranion istetrakis(3,5-bis(tifluoromethyl)phenyl)borate (i.e. BAr^(F) ₄ ⁻). In oneembodiment, the catalyst is the (allyl)(mesitylene)Ni(II)⁺ BAr^(F) ₄ ⁻complex as shown in formula II

The polymerization using the (allyl)(arene)Ni(II) catalysts may be donefollowing the methods as described in O'Connor et al. (Journal ofApplied Polymer Science, Part A: Polymer Chemistry, Vol. 48, 1901-1912(2010)). The copolymerization may be carried out by solutionpolymerization at a temperature ranging from 0 to 60° C. Suitablesolvents for the solution polymerization include toluene, methylenechloride, and heptane, and the like.

The copolymer may be compounded into a rubber composition.

The rubber composition may optionally include, in addition to thefunctionalized copolymer, one or more rubbers or elastomers containingolefinic unsaturation. The phrases “rubber or elastomer containingolefinic unsaturation” or “diene based elastomer” are intended toinclude both natural rubber and its various raw and reclaim forms aswell as various synthetic rubbers. In the description of this invention,the terms “rubber” and “elastomer” may be used interchangeably, unlessotherwise prescribed. The terms “rubber composition,” “compoundedrubber” and “rubber compound” are used interchangeably to refer torubber which has been blended or mixed with various ingredients andmaterials and such terms are well known to those having skill in therubber mixing or rubber compounding art. Representative syntheticpolymers are the homopolymerization products of butadiene and itshomologues and derivatives, for example, methylbutadiene,dimethylbutadiene and pentadiene as well as copolymers such as thoseformed from butadiene or its homologues or derivatives with otherunsaturated monomers. Among the latter are acetylenes, for example,vinyl acetylene; olefins, for example, isobutylene, which copolymerizeswith isoprene to form butyl rubber; vinyl compounds, for example,acrylic acid, acrylonitrile (which polymerize with butadiene to formNBR), methacrylic acid and styrene, the latter compound polymerizingwith butadiene to form SBR, as well as vinyl esters and variousunsaturated aldehydes, ketones and ethers, e.g., acrolein, methylisopropenyl ketone and vinylethyl ether. Specific examples of syntheticrubbers include neoprene (polychloroprene), polybutadiene (includingcis-1,4-polybutadiene), polyisoprene (including cis-1,4-polyisoprene),butyl rubber, halobutyl rubber such as chlorobutyl rubber or bromobutylrubber, styrene/isoprene/butadiene rubber, copolymers of 1,3-butadieneor isoprene with monomers such as styrene, acrylonitrile and methylmethacrylate, as well as ethylene/propylene terpolymers, also known asethylene/propylene/diene monomer (EPDM), and in particular,ethylene/propylene/dicyclopentadiene terpolymers. Additional examples ofrubbers which may be used include alkoxy-silyl end functionalizedsolution polymerized polymers (SBR, PBR, IBR and SIBR), silicon-coupledand tin-coupled star-branched polymers. The preferred rubber orelastomers are polyisoprene (natural or synthetic), polybutadiene andSBR.

In one aspect the at least one additional rubber is preferably of atleast two of diene based rubbers. For example, a combination of two ormore rubbers is preferred such as cis 1,4-polyisoprene rubber (naturalor synthetic, although natural is preferred), 3,4-polyisoprene rubber,styrene/isoprene/butadiene rubber, emulsion and solution polymerizationderived styrene/butadiene rubbers, cis 1,4-polybutadiene rubbers andemulsion polymerization prepared butadiene/acrylonitrile copolymers.

In one aspect of this invention, an emulsion polymerization derivedstyrene/butadiene (E-SBR) might be used having a relatively conventionalstyrene content of about 20 to about 28 percent bound styrene or, forsome applications, an E-SBR having a medium to relatively high boundstyrene content, namely, a bound styrene content of about 30 to about 45percent.

By emulsion polymerization prepared E-SBR, it is meant that styrene and1,3-butadiene are copolymerized as an aqueous emulsion. Such are wellknown to those skilled in such art. The bound styrene content can vary,for example, from about 5 to about 50 percent. In one aspect, the E-SBRmay also contain acrylonitrile to form a terpolymer rubber, as E-SBAR,in amounts, for example, of about 2 to about 30 weight percent boundacrylonitrile in the terpolymer.

Emulsion polymerization prepared styrene/butadiene/acrylonitrilecopolymer rubbers containing about 2 to about 40 weight percent boundacrylonitrile in the copolymer are also contemplated as diene basedrubbers for use in this invention.

The solution polymerization prepared SBR (S-SBR) typically has a boundstyrene content in a range of about 5 to about 50, preferably about 9 toabout 36, percent. The S-SBR can be conveniently prepared, for example,by organo lithium catalyzation in the presence of an organic hydrocarbonsolvent.

In one embodiment, cis 1,4-polybutadiene rubber (BR) may be used. SuchBR can be prepared, for example, by organic solution polymerization of1,3-butadiene. The BR may be conveniently characterized, for example, byhaving at least a 90 percent cis 1,4-content.

The cis 1,4-polyisoprene and cis 1,4-polyisoprene natural rubber arewell known to those having skill in the rubber art.

The term “phr” as used herein, and according to conventional practice,refers to “parts by weight of a respective material per 100 parts byweight of rubber, or elastomer.”

The rubber composition may also include up to 70 phr of processing oil.Processing oil may be included in the rubber composition as extendingoil typically used to extend elastomers. Processing oil may also beincluded in the rubber composition by addition of the oil directlyduring rubber compounding. The processing oil used may include bothextending oil present in the elastomers, and process oil added duringcompounding. Suitable process oils include various oils as are known inthe art, including aromatic, paraffinic, naphthenic, vegetable oils, andlow PCA oils, such as MES, TDAE, SRAE and heavy naphthenic oils.Suitable low PCA oils include those having a polycyclic aromatic contentof less than 3 percent by weight as determined by the IP346 method.Procedures for the IP346 method may be found in Standard Methods forAnalysis & Testing of Petroleum and Related Products and BritishStandard 2000 Parts, 2003, 62nd edition, published by the Institute ofPetroleum, United Kingdom.

The rubber composition may include silica, carbon black, or acombination of silica and carbon black.

The rubber composition may include from about 1 to about 150 phr ofsilica. In another embodiment, from 10 to 100 phr of silica may be used.

The commonly employed siliceous pigments which may be used in the rubbercompound include conventional pyrogenic and precipitated siliceouspigments (silica). In one embodiment, precipitated silica is used. Theconventional siliceous pigments employed in this invention areprecipitated silicas such as, for example, those obtained by theacidification of a soluble silicate, e.g., sodium silicate.

Such conventional silicas might be characterized, for example, by havinga BET surface area, as measured using nitrogen gas. In one embodiment,the BET surface area may be in the range of about 40 to about 600 squaremeters per gram. In another embodiment, the BET surface area may be in arange of about 80 to about 300 square meters per gram. The BET method ofmeasuring surface area is described in the Journal of the AmericanChemical Society, Volume 60, Page 304 (1930).

The conventional silica may also be characterized by having adibutylphthalate (DBP) absorption value in a range of about 100 to about400, alternatively about 150 to about 300.

The conventional silica might be expected to have an average ultimateparticle size, for example, in the range of 0.01 to 0.05 micron asdetermined by the electron microscope, although the silica particles maybe even smaller, or possibly larger, in size.

Various commercially available silicas may be used, such as, only forexample herein, and without limitation, silicas commercially availablefrom PPG Industries under the Hi-Sil trademark with designations 210,243, etc.; silicas available from Rhodia, with, for example,designations of Z1165MP and Z165GR and silicas available from Degussa AGwith, for example, designations VN2 and VN3, etc.

Commonly employed carbon blacks can be used as a conventional filler incombination with silica in an amount ranging from 1 to 150 phr. Inanother embodiment, from 10 to 100 phr of carbon black may be used.Although carbon black may be used with silica, in one embodiment,essentially no carbon black is used except for an amount required toimpart black color to the tire which is from 1 to 10 phr. Representativeexamples of such carbon blacks include N110, N121, N134, N220, N231,N234, N242, N293, N299, N315, N326, N330, N332, N339, N343, N347, N351,N358, N375, N539, N550, N582, N630, N642, N650, N683, N754, N762, N765,N774, N787, N907, N908, N990 and N991. These carbon blacks have iodineabsorptions ranging from 9 to 145 g/kg and DBP number ranging from 34 to150 cm³/100 g.

Combinations of silica and carbon black may be used in the composition.In one embodiment, the weight ratio of silica to carbon black is greaterthan or equal to one.

Other fillers may be used in the rubber composition including, but notlimited to, particulate fillers including ultra high molecular weightpolyethylene (UHMWPE), crosslinked particulate polymer gels includingbut not limited to those disclosed in U.S. Pat. Nos. 6,242,534;6,207,757; 6,133,364; 6,372,857; 5,395,891; or 6,127,488, andplasticized starch composite filler including but not limited to thatdisclosed in U.S. Pat. No. 5,672,639. Such other fillers may be used inan amount ranging from 1 to 30 phr.

In one embodiment the rubber composition may contain a conventionalsulfur containing organosilicon compound. In one embodiment, the sulfurcontaining organosilicon compounds are the 3,3′-bis(trimethoxy ortriethoxy silylpropyl)polysulfides. In one embodiment, the sulfurcontaining organosilicon compounds are3,3′-bis(triethoxysilylpropyl)disulfide and/or3,3′-bis(triethoxysilylpropyl)tetrasulfide.

In another embodiment, suitable sulfur containing organosiliconcompounds include compounds disclosed in U.S. Pat. No. 6,608,125. In oneembodiment, the sulfur containing organosilicon compounds includes3-(octanoylthio)-1-propyltriethoxysilane,CH₃(CH₂)₆C(═O)—S—CH₂CH₂CH₂Si(OCH₂CH₃)₃, which is available commerciallyas NXT™ from Momentive Performance Materials.

In another embodiment, suitable sulfur containing organosiliconcompounds include those disclosed in U.S. Patent Publication No.2003/0130535. In one embodiment, the sulfur containing organosiliconcompound is Si-363 from Degussa.

The amount of the sulfur containing organosilicon compound in a rubbercomposition will vary depending on the level of other additives that areused. Generally speaking, the amount of the compound will range from 0.5to 20 phr. In one embodiment, the amount will range from 1 to 10 phr.

It is readily understood by those having skill in the art that therubber composition would be compounded by methods generally known in therubber compounding art, such as mixing the various sulfur-vulcanizableconstituent rubbers with various commonly used additive materials suchas, for example, sulfur donors, curing aids, such as activators andretarders and processing additives, such as oils, resins includingtackifying resins and plasticizers, fillers, pigments, fatty acid, zincoxide, waxes, antioxidants and antiozonants and peptizing agents. Asknown to those skilled in the art, depending on the intended use of thesulfur vulcanizable and sulfur-vulcanized material (rubbers), theadditives mentioned above are selected and commonly used in conventionalamounts. Representative examples of sulfur donors include elementalsulfur (free sulfur), an amine disulfide, polymeric polysulfide andsulfur olefin adducts. In one embodiment, the sulfur-vulcanizing agentis elemental sulfur. The sulfur-vulcanizing agent may be used in anamount ranging from 0.5 to 8 phr, alternatively with a range of from 1.5to 6 phr. Typical amounts of tackifier resins, if used, comprise about0.5 to about 10 phr, usually about 1 to about 5 phr. Typical amounts ofprocessing aids comprise about 1 to about 50 phr. Typical amounts ofantioxidants comprise about 1 to about 5 phr. Representativeantioxidants may be, for example, diphenyl-p-phenylenediamine andothers, such as, for example, those disclosed in The Vanderbilt RubberHandbook (1978), Pages 344 through 346. Typical amounts of antiozonantscomprise about 1 to 5 phr. Typical amounts of fatty acids, if used,which can include stearic acid comprise about 0.5 to about 3 phr.Typical amounts of zinc oxide comprise about 2 to about 5 phr. Typicalamounts of waxes comprise about 1 to about 5 phr. Often microcrystallinewaxes are used. Typical amounts of peptizers comprise about 0.1 to about1 phr. Typical peptizers may be, for example, pentachlorothiophenol anddibenzamidodiphenyl disulfide.

Accelerators are used to control the time and/or temperature requiredfor vulcanization and to improve the properties of the vulcanizate. Inone embodiment, a single accelerator system may be used, i.e., primaryaccelerator. The primary accelerator(s) may be used in total amountsranging from about 0.5 to about 4, alternatively about 0.8 to about 1.5,phr. In another embodiment, combinations of a primary and a secondaryaccelerator might be used with the secondary accelerator being used insmaller amounts, such as from about 0.05 to about 3 phr, in order toactivate and to improve the properties of the vulcanizate. Combinationsof these accelerators might be expected to produce a synergistic effecton the final properties and are somewhat better than those produced byuse of either accelerator alone. In addition, delayed actionaccelerators may be used which are not affected by normal processingtemperatures but produce a satisfactory cure at ordinary vulcanizationtemperatures. Vulcanization retarders might also be used. Suitable typesof accelerators that may be used in the present invention are amines,disulfides, guanidines, thioureas, thiazoles, thiurams, sulfenamides,dithiocarbamates and xanthates. In one embodiment, the primaryaccelerator is a sulfenamide. If a second accelerator is used, thesecondary accelerator may be a guanidine, dithiocarbamate or thiuramcompound.

The mixing of the rubber composition can be accomplished by methodsknown to those having skill in the rubber mixing art. For example, theingredients are typically mixed in at least two stages, namely, at leastone non-productive stage followed by a productive mix stage. The finalcuratives including sulfur-vulcanizing agents are typically mixed in thefinal stage which is conventionally called the “productive” mix stage inwhich the mixing typically occurs at a temperature, or ultimatetemperature, lower than the mix temperature(s) than the precedingnon-productive mix stage(s). The terms “non-productive” and “productive”mix stages are well known to those having skill in the rubber mixingart. The rubber composition may be subjected to a thermomechanicalmixing step. The thermomechanical mixing step generally comprises amechanical working in a mixer or extruder for a period of time suitablein order to produce a rubber temperature between 140° C. and 190° C. Theappropriate duration of the thermomechanical working varies as afunction of the operating conditions, and the volume and nature of thecomponents. For example, the thermomechanical working may be from 1 to20 minutes.

The rubber composition may be incorporated in a variety of rubbercomponents of the tire. For example, the rubber component may be a tread(including tread cap and tread base), sidewall, apex, chafer, sidewallinsert, wirecoat or innerliner. In one embodiment, the component is atread.

The pneumatic tire of the present invention may be a race tire,passenger tire, aircraft tire, agricultural, earthmover, off-the-road,truck tire, and the like. In one embodiment, the tire is a passenger ortruck tire. The tire may also be a radial or bias.

Vulcanization of the pneumatic tire of the present invention isgenerally carried out at conventional temperatures ranging from about100° C. to 200° C. In one embodiment, the vulcanization is conducted attemperatures ranging from about 110° C. to 180° C. Any of the usualvulcanization processes may be used such as heating in a press or mold,heating with superheated steam or hot air. Such tires can be built,shaped, molded and cured by various methods which are known and will bereadily apparent to those having skill in such art.

This invention is illustrated by the following examples that are merelyfor the purpose of illustration and are not to be regarded as limitingthe scope of the invention or the manner in which it can be practiced.Unless specifically indicated otherwise, parts and percentages are givenby weight.

Example 1

Synthesis of the Ni catalyst II is described in literature (O'Connor etal. Organometallics 2009, 28 2372-2384). Alternatively, a mixture ofthis complex with Mg-salts and excess NaBAr^(F) ₄ can be generated byfollowing the outlined procedure of example 2.

Example 2

In this example, the synthesis of a Ni(II) coordination catalyst isillustrated. The compound of formula III was converted to the compoundof formula II as follows. Compound III (8 mmol) was combined withNaBAr^(F) ₄ (8 mmol) and mesitylene (20 mmol) in 40 ml of diethyl etherin a 100 ml Schlenk tube and cooled −78 C. After 5 minutes, 8 ml of 1 Mallyl magnesium bromide in diethyl ether was dropwise added understirring, and the temperature increased to −20 C by exchange of thecooling bath after the addition of allyl magnesium bromide was complete.After 60 minutes at −20 C, the cooling bath was removed and the mixturewarmed to 25 C at which the ether was distilled off at 25 C to leave acrude solid. Methylene chloride (30 ml) was then added and the mixturewas agitated, followed by filtration of the solids. Heptane (10 mL) wasadded to the methylene chloride solution and the resulting mixtureconcentrated to dryness under high vacuum to leave 6.85 g of solidscontaining about 50% yield of the catalyst II based on Ni.

Example 3

In the following example, the copolymerization of 1,3 butadiene with(E)-4,4,5,5-tetramethyl-2-(3-methylbuta-1,3-dien-1-yl)-1,3,2-dioxaborolane(formula IV) is illustrated.

(E)-4,4,5,5-tetramethyl-2-(3-methylbuta-1,3-dien-1-yl)-1,3,2-dioxaborolane

The functional monomer(E)-4,4,5,5-tetramethyl-2-(3-methylbuta-1,3-dien-1-yl)-1,3,2-dioxaborolanemay be synthesized following methods as described in Chemistry—AEuropean Journal (2013), 19, (28), 9127-9131. Alternatively,(E)-4,4,5,5-tetramethyl-2-(3-methylbuta-1,3-dien-1-yl)-1,3,2-dioxaborolanecan be synthesized in optimized yield by the following procedure

Synthesis of 2-methylbut-1-en-3-yne

According to Defranq, E.; Zesiger, T.; Tabacchi, R. Helv. Chim. Acta1993, 76, 425-430.: 215 g 2-methyl-3-yn-2-ol (2.5 mol, 1 equiv.) werefilled into a 1 L three-necked flask, equipped with a dropping funneland a distillation apparatus. The receiver flask was cooled to −78° C.319 g acetic anhydride (3.13 mol, 1.25 equiv.) and 12 g sulfuric acid(0.12 mol, 0.05 equiv.) were filled into the dropping funnel and addeddropwise over 2 hours starting at 50° C. After addition of 50 mL thetemperature was increased to 70° C. and distillation of the productbegan (bp.: 33° C./1 atm). After complete addition the temperature wasincreased to 80° C. The product was washed with ice water to removeresidues of acetic acid and alcohol and dried with sodium sulfate.

Yield: 55% (90 g, 1.36 mol, related to 2-methyl-3-yn-2-ol), clear liquid

¹H NMR (400 MHz, 25° C., CDCl₃): δ 5.38 (m, 1H, H−3), 5.29 (m, 1H, H−3),2.86 (s, 1H, H−2), 1.90 (t, ⁴J₁₋₃=1.3 Hz, 3H, H−1).

Synthesis of(E)-4,4,5,5-tetramethyl-2-(3-methylbuta-1,3-dien-1-yl)-1,3,2-dioxaborolane

In analogy to a procedure published by Hoveyda et al. hydroborylation of2-methylbut-1-en-3-yne was accomplished under copper catalysis (Lee, Y.;Jang, H.; Hoveyda, A. H. J. Am. Chem. Soc. 2009, 131, 18234-18235): 3.8g (30 mmol, 1 equiv.) pinacolborane, 2.2 g 2-methylbut-1-en-3-yne (33mmol, 1.1 equiv), 4 mg (10 μmol, 0.3 mol %)1,3-(2,6-di-isopropyl-phenyl)imidazolidin-2-ylidene)copper(I) chlorideand 8 mg (13 mol, 0.4 mol %) lithium tert-butoxide were stirred underexclusion of water and oxygen for 2 days. The volatiles were removed invacuum and the residue purified via bulb to bulb distillation.

Yield: quantitative

¹H NMR (400 MHz, 25° C., C₆D₆): δ=7.47 (d, ³J₄₋₃=18 Hz, 1H, H4), 5.82(dt, ³J₃₋₄=18 Hz, ⁴J₃₋₁=0.5 Hz, 1H, H3), 4.90-5.05 (m, 2H, H1), 1.68 (m,3H, H7), 1.09 (m, 12H, H6)

¹³C NMR (400 MHz, 25° C., C₆D₆): δ=152.7 (C3), 143.4 (C2), 120.0 (C1),117.2 (b, C4), 83.1 (C5), 24.9 (C6), 17.7 (C7).

Example 4

In this example, the copolymerization of 1,3 butadiene with the monomerof formula IV is illustrated. Polymerizations were done to produce fourcopolymer samples, as indicated in Table 1.

The functional monomer of formula IV was synthesized as described inExample 3.

The monomer of formula IV was added to a flame-dried schlenk-flask astoluene solution (total volume of toluene 15 mL for example 1-3, and 35mL for example 4) and the flask was subsequently sealed with a rubberseptum. Butadiene was added, either by condensation into the toluene at−78° C. (samples 1-3) or by saturation of the toluene at the reactiontemperature (sample 4). The polymerization was initiated by adding thecatalyst in toluene (5 mL) at the indicated reaction temperature. Thepolymerization was allowed to run at that temperature for the indicatedtime. 0.5 mL of NEt₃ were added to end the polymerization. Residualbutadiene was carefully removed under reduced pressure and the polymerwas precipitated in MeOH in the presence of BHT (ca. 100 mg/100 mL). Theformed polymer was dried overnight at 50° C. under reduced pressure togive the indicated yield g ofpoly(butadiene-co-(E)-4,4,5,5-tetramethyl-2-(3-methylbuta-1,3-dien-1-yl)-1,3,2-dioxaborolane).Samples were analyzed with results given in Table 1. Molecular weight Mnand polydispersity (PDI) were measured using GPC in THF vs. polystyrenestandards. Glass transition temperature Tg was measured using DSC. Themicrostructure of the polymer was determined by NMR-analyses (¹H and¹³C).

Sample No. 1 2 3 4 amount of catalyst¹, μmol 10 + 10 10 10 + 15 6temperature, ° C. 0 r.t. r.t. 0 time, hr 1 1 5.5 4 butadiene, g 9.1 10.39.0 1.05 Bar comonomer of formula IV, mmol 0.52 2.06 5.18 0.43 yield, g5.7 4.9 7.7 13.2 comonomer incorporation, mol % 0.43 1.85 3.6 0.175comonomer conversion, % 87 81 99 99 M_(n), 10³ g/mol 65 37 25 140 PDI2.6 2.4 2 1.9 T_(g), ° C. −97 −95 −92 −96 Microstructure, % 1,4 cis 9696 95 96 ¹Catalyst was added in two aliquots in samples 1 and 3 asindicated

What is claimed is:
 1. A copolymer of a first monomer selected from thegroup consisting of 1,3-butadiene and isoprene, and a second monomer


2. The copolymer of claim 1, comprising from 0.1 to 40 percent by weightof units derived from the second monomer, based on the weight of thecopolymer.
 3. The copolymer of claim 1, comprising from 0.5 to 20percent by weight of units derived from the second monomer based on theweight of the copolymer.
 4. The copolymer of claim 1, comprising from 1to 5 percent by weight of units derived from the second monomer based onthe weight of the copolymer.
 5. A rubber composition comprising thecopolymer of claim
 1. 6. A pneumatic tire comprising the rubbercomposition of claim
 5. 7. A method of making a copolymer, comprisingthe step of polymerizing a monomer selected from the group consisting of1,3-butadiene and isoprene and the monomer


8. The method of claim 7 wherein the polymerization is done in thepresence of a catalyst of formula II

where BAr^(F) ₄ ⁻ is tetrakis(3,5-bis(trifluoromethyl)phenyl) borate.